Telecommunications systems, cable television systems and data communication networks use optical networks to rapidly convey large amounts of information between remote points. In an optical network, information is conveyed in the form of optical signals through optical fibers. Optical fibers comprise thin strands of glass capable of communicating the signals over long distances with very low loss. An optical network may be configured to combine modulated signals at various wavelengths or optical frequencies (also known as “channels”) into a single optical fiber. Each disparate channel may include optically encoded information to be communicated throughout the optical network. Such combining of various channels into a single fiber is known as wavelength-division multiplexing (WDM). Dense wavelength division multiplexing (DWDM) refers to multiplexing a larger (denser) number of wavelengths, usually greater than forty, into a fiber. WDM, DWDM, or other multi-wavelength transmission techniques are employed in optical networks to increase the aggregate bandwidth per optical fiber. Without WDM or DWDM, the bandwidth in networks would be limited to the bit rate of solely one wavelength. With more bandwidth, optical networks are capable of transmitting greater amounts of information.
Optical networks may be using any one or a number of topologies, including mesh networks, point-to-point networks, ring networks, and others. A ring network is a network topology in which each node connects to exactly two other nodes, forming a single continuous pathway for signals through each node—a ring. Data travels from node to node, with each node along the way handling every packet.
Optical networks often employ redundancies to maximize performance and availability. In ring networks, such redundancies may include shared ring protection schemes such as bidirectional line switched ring (BLSR). With BLSR, rather than sending redundant copies of packets from ingress to egress, ring nodes adjacent to a failure may reroute traffic in an opposite direction of the ring in response to a failure. For example, if a failure occurs at a first node intermediate to a second node and a third node in which the first node and second node are “counterclockwise” to the third node, third node may reroute traffic intended for the second node in a “clockwise” direction (e.g., via nodes other than the first node).
To reduce network cost and complexity, it is often desirable to employ demand aggregation in an optical network. In general, demand aggregation may refer to aggregating multiple lower rate traffic demands (e.g., bandwidth requests between two nodes) into higher rate WDM or DWDM channels such that equipment cost and complexity is minimized. To illustrate, a demand typically requires an optical line card (OLC) with an add-drop multiplexer to be allocated at the source and destination nodes of the demand. Because an OLC may be capable of aggregating multiple demands, sharing multiple demands among OLCs may reduce the total number of OLCs required for a give set of demands. In addition, multiple OLCs may be assigned to the same WDM or DWDM ring to reduce the total number of wavelengths used. Because network cost is typically driven by the number of OLCs and wavelengths, minimizing OLC and wavelength usage with demand aggregation may reduce network cost.
Existing approaches to demand aggregation in shared ring networks have disadvantages. For example, some traditional approaches split demand into separate rings or split over to another ring for better bandwidth utilization. Other approaches consider only the case of uniform traffic or assume routing is given. However, for practical applications, a demand aggregation approach is desired that supports non-uniform traffic demands, in which routing of each demand is not given, and demands cannot be split or switched over to another ring.